This invention relates to hose coupling inserts of the type utilizing crimped sleeve and nipple insert assemblies for use on flexible hose ends. More particularly, the invention relates to the construction of nipple inserts utilized in such assemblies, particularly for use with elastomeric hose materials.
In the prior art, it has been commonplace to employ nipple inserts containing barbs designed to grip the "innertubing" of hose ends for purposes of coupling such ends to relatively movable hydraulic apparatus, such as that employed in back hoe and front end loaders. Such nipple inserts are first inserted into hose ends, and sleeves are mounted thereover, whereupon the sleeves are crimped circumferentially about the hose ends for assuring permanent coupling of the hose ends to the nipple inserts. The barbs elastically, and in some cases plastically, distort and displace selective portions of the innertubing. A balance must, however, be achieved in the coupling mechanism involved. The barbs must be designed in a manner to adequately secure the hose to the insert; yet, stress tears, which can propagate and result in fracture of the hose, must be assiduously avoided.
Several designs have employed barbs which include axially directed tips adapted to make a "controlled" cut into the hose liner, thus avoiding undesirable tearing and resultant fracture of the rubber. One of such designs even provides a controlled leakage path in an environment utilizing a plurality of such tips, wherein a labyrinth-style mechanism is effective to avoid leakage as a function of system pressure. Such designs however are relatively complex, and unless sized properly can cause more problems than they are designed to solve. More preferable is a design which avoids high stress areas altogether. Such designs are predicated on the premise that if high stress areas are avoided, such stress areas will not propagate, and premature fractures, hence failures, can be more effectively avoided.